The effects of high hydrostatic pressure on a marine crustacean, on the crustacean abdominal nerve cord and another nerve bundle

• Main Author: Wilcock, Sylvia E.
• Published: University of Aberdeen 1979
• Subjects: 571.1
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.477242

The locomotory response of the decapod, crangon crangon, to high hydrostatic pressure has been investigated by an observational method. It was found that the shrimp exhibits sensitivity to high pressure by becoming hyperactive and undergoing 'convulsions' And 'tail-twitches'. The onset of such a convulsive phase was, + 5-2 On average, (51.7 - 3.1) x 10 n.m. (N = 22) when compressed At a rate of 103.4 x 10[superscript5] n.m. -2 Hr.-1, But this was lowered to + 5-2 (34.5 - 5.1) X 10 n.m. (N = 5) when compressed at only 5~2~1 20.7 X 10 n.m. Hr. Shrimps with the ventral nerve cord Cut in the rostral portion of the abdomen, exhibited convulsions at approximately 2.5 times that in intact animals. Homarus gammarvs, a common lobster, exhibited similar Behaviour to the shrimp when exposed to high pressure. A compression rate of 103.4 x 10 n'.m.~ hr-1. resulted in an onset Of vigorous tail-flip activity at a mean pressure level of (92.3. - 10.7) X 10n.m. (N = 9). When compressed at 5-2-I 20.7 X 10 n.m. Hr.,The mean pressure at which this hyper-I c - 2 activity began, was lowered to (53.8 - 18.6) x 10 [Special character omitted] n.m., Although the activity was not vigorous and often only involved flaring of the uropods and slow flexing of the tail. When the crustaceans were maintained at a specific Pressure level over several hours, adaptation to pressure was Only observed at the moderate pressures (51.7 x 62.0) x 10 -2.N.m.. This was indicated by a decline in convulsive activity. At higher pressures convulsive activity declined, but repression of all muscular activity was evident. At lower pressures, long exposure led to the onset of. Convulsive activity. This was illustrated by c. crangon. Transecting the abdominal ventral nerve cord caudal to the point of recording (inn. gammarus), tail-flip activity was induced by pressure within the normal range. The mean convulsion threshold pressure level was (89.5 - 8.6) x 10 N.m.(n =6). However, transecting the nerve cord rostral to the point of recording led to an inability of the animals to flex their abdomens. Hyperactivity was evident by twitching in the anterior appendages, by rapid pleopod movement and by fanning of the uropods. In a group of six animals, this started to occur at approximately 93.1 x 10 N.m. By implantation of silver/silver chloride bipolar electrodes, "in vivo, on the abdominal ventral nerve cord, spontaneous nerve action potentials were recorded from the intact nerve, during compression of the animal, at the period when the animal was undergoing convulsive activity. Such spontaneous activity was net recorded when the electrodes were placed caudal to a transection of the transected nerve cord. Pressure also changed the shape of the evoked' compound action potential, however not all the changes were statistically significant. The general trend was that on compression to 2.06,8 x 105 N.m.-2 the threshold stimulus strength increased, the amplitude of the compound action potential decreased [Special character omitted] and the duration and delay of the peak of the compound action potential from the. stimulus artefact also increased. The isolated sciatic nerve of frog was used to compare the effects of hydrostatic pressure on the compound action potential, evoked in the purely axonal nerve bundle, with that evoked in the more complex synaptically interrupted nerve cord of h. gammarus. High hydrostatic pressure affected the evoked compound of the axonal nerve bundle in the same way it affected that of the lobster ventral nerve cord. In addition it was found that low temperature conditions (particularly below 14°C) augmented the effects of high pressure on the action potential. The results of these electrophysiological studies were compared with the observations made of the High Pressure Nervous Syndrome in decapods. Both excitatory and depressant effects were discussed, with reference to the relevant literature. Future experiments leading from this investigation were also discussed.